Magneto failure at 9000ft

[carusoam]

Thanks, Cliffy!

Falling apart vs. falling off may be technically different.  But they do have some similarities...

Thanks for the detailed explanation...

Best regards,

-a-

 

[jetdriven]

They’re a single split washer and I’ve never seen them replaced, and I’ve never seen one properly torqued come loose either. 

 Btw this is a magneto mounting nut  installed at a well-known (not west coast) MSC. They say it’s better. I’m not convinced. 

 

[cliffy]

I've never seen a NEW properly torqued star washer come loose either. 

[jasona900]

2 hours ago, jetdriven said:

They’re a single split washer and I’ve never seen them replaced, and I’ve never seen one properly torqued come loose either. 

 Btw this is a magneto mounting nut  installed at a well-known (not west coast) MSC. They say it’s better. I’m not convinced. 

 

I just had a 500hr inspection on my mags.. the MSC told me that split washers were installed prior to removal for inspection.  They told me that is not correct, and star washers should be used.  There is a SB that also reccomends use of star washers.

[Guest]

2 hours ago, jasona900 said:

I just had a 500hr inspection on my mags.. the MSC told me that split washers were installed prior to removal for inspection.  They told me that is not correct, and star washers should be used.  There is a SB that also reccomends use of star washers.

Normally Lycoming engine use internal star lock washers and Continental engines use split lock washers.  Either would be acceptable as long as the nut is in safety(thread of the stud or bolt through the nut) 

Re-use of old locking devise seems common and a leading cause of failure.

Clarence

[jetdriven]

There’s also no flat washer, if you look the nut split the ends of the split lock washer beucause if this. Also the torque seal goes Over the threads of the stud which can strip out the stud.  The pilot was complaining about an uneven mag drop, and Checking the mag timing revealed why. One was set at 21 degrees and one was at 23.  The shop claims they were set at 25.0 degrees when it flew away 43 hours prior. 

Edited March 30, 2018 by jetdriven

[cliffy]

Did the shop put the torque seal on? :-)  It looks like it was put on at engine assembly or else the shop had the same color TS. And the same guy installing it incorrectly.

Here's a note (clipped from the web)on how to use TS-

Important Note: “Torque Seal” must NEVER be put directly on to the thread of a nut or bolt. Getting torque seal on the thread can mean the bolt may need to be cut off and completely replaced

As correctly noted above by jetdriven.

[Gary0747]

Do you mean the lock washers should be changed every time the timing gets adjusted a degree or two?

[cliffy]

YUP!!!!   Any time the nuts are loosened a new lock washer needs to be installed. Once tightened the washers take  "set" and never lock well again. 

If you loosen and retighten you ARE reusing a locking device. Something we don't want to do. 

I never loosen a mag without replacing the lock washers with new ones. 

[ArtVandelay]

Can someone explain why they aren’t safety wired?

[Gary0747]

Would seem to be easier to have a double nut with the lock washer on the outer nut?  Totally removing the lone nut to replace the lock washer runs the risk of the mag slipping out or just the retainer falling out?

[Guest]

On the D2000/3000 series magneto I also install a “Pal nut” on top of the regular nut as an additional safety device. 

Clarence

[jetdriven]

7 hours ago, cliffy said:

YUP!!!!   Any time the nuts are loosened a new lock washer needs to be installed. Once tightened the washers take  "set" and never lock well again. 

If you loosen and retighten you ARE reusing a locking device. Something we don't want to do. 

I never loosen a mag without replacing the lock washers with new ones. 

Yes.  Always replace these star lock washers. If you’re  not 100% certain they’ve been changed, insist Ithey are changed while you wait. Yes it’s that important. 

Edited March 31, 2018 by jetdriven

[PTK]

https://www.lycoming.com/sites/default/files/Dual Magneto Attachment.pdf

[jetdriven]

Follow that like your life depends on it, because it does.

[Gary0747]

Is the Lycoming lock washer STD475 to be used on all Lycoming mags?  It must be very special at $1.40 ea?

[cliffy]

Pal nuts used to be used on all engine case bolts and cylinder hold down nuts 4 decades ago. They work well. 

[jetdriven]

3 hours ago, Gary0747 said:

Is the Lycoming lock washer STD475 to be used on all Lycoming mags?  It must be very special at $1.40 ea?

It is a standard star lock washer.  5/16”. Evidently the flat washer is not the standard AN960 though.  Perhaps a little thicker. 

Edited March 31, 2018 by jetdriven

[201er]

On 3/30/2018 at 1:12 AM, jetdriven said:

They’re a single split washer and I’ve never seen them replaced, and I’ve never seen one properly torqued come loose either. 

 Btw this is a magneto mounting nut  installed at a well-known (not west coast) MSC. They say it’s better. I’m not convinced. 

 

Now why would an MSC possibly do that!? They specialize in Mooney’s so you’d think they would be familiar with the SB. And they’ll charge you an arm and a leg while they’re at it!

[Guest]

7 hours ago, Gary0747 said:

Is the Lycoming lock washer STD475 to be used on all Lycoming mags?  It must be very special at $1.40 ea?

It’s the same as an MS35333-41, a few pennies at Spruce.

Clarence

[cliffy]

I buy'm by the 100.